1. Field of the Invention
The invention relates to characterization of signal integrity on data output paths in a DRAM memory, and more particularly, to characterization of signal integrity on data output paths by bypassing the main array and reading data from a series of registers. The invention applies to a much broader variety of chip-to-chip interfaces, however.
2. Description of the Prior Art
Characterization of a memory interface is a crucial part of the manufacturing process. Certain parameters are set and tested in order to gauge a full operational view of the memory array, and how it operates under different conditions.
Particular design challenges are associated with Input/Output (I/O) signaling. At low speeds, problems generally only occur where transmission lines are especially long. At high speeds, however, even the shortest transmission lines can suffer from problems such as inter-symbol interference and crosstalk, due to high frequency effects.
In order to test memory read signal integrity on a number of data output paths, data patterns are written to the main array, and then read out. As the array needs to be accessed for this read operation, a certain amount of noise will be added, and the data path timing may be limited by the array timing, which makes characterization of the I/O scheme difficult.
It is therefore an objective to perform data characterization of data output paths without having to access the array.